Investigating the Role of Loose Stone Dams in Controlling the Sedimentation of Oak Forest Area in the West of Iran

Loose stone check dams are among the least expensive structures in watersheds and are usually used to protect soil resources and reduce sediment transfer in small waterways. The effectiveness of these dams has received less attention from researchers in particle deposition in the forest area. The purpose of this study was investigating the effect of loose stone check dams and the role of the factors affecting on the amount of sedimentation in the forest area. Also, grading of sediments were studied at consecutive dams and different distances from each dam and compared with the soil particle size distribution of upstream soil. In this research the eleven loose stone check dams follow each other were investigated in the Marg watershed located in the southwest of Kermanshah. These dams have been constructed in the second order waterways during the year 2016. The results showed the upper dams of the waterway had the highest amount (9245 kg h-1) and the lower dams had the lowest amount of sediment (3575 kg h-1). The sediment amount of the back dams was directly affected by the slope and area of the dam drainage area. The amount of sand was 1.5 higher than the upstream soil, while the amount of silt and clay in the sediment samples was lower of the upstream soil, 75.5% and 23.8%, respectively. The amount of sand particles increases but the silt and clay particles had a declining trend with distance from the dam during the sedimentation surface. This study showed that loose Stone dams play an important role in sedimentation of coarse particles and they are one of the important structures in the watershed to prevent sediment transfer due to the low cost of their construction. Although, the construction of low drainage dams is necessary to prevent the transfer of fine particles.